Gray cast iron and the process for its production



Patented Dec, 8, 1925.

UNITED STATES 1,564,284 PATENT OFFICE.

KARL srrr, or

MANNHEIM, GERMANY, ASSIGNOR TO THE EIRM HEINRICH LANZ, OI

MANNHEIM, BADEN, GERMANY, A COPARTNERSHIP.

GRAY CAST IRON AND THE PROCESS FOR ITS PRODUCTION.

No Drawing.

1 all whom it may concern:

Be it known that I, KARL SIPP, a citizen of Germany, and a resident ofMannheim, Baden, Germany, have invented certain new and usefulImprovements in Gray Cast Iron and the Process for its Production, ofwhich the following is a specification. Y

My present invention relates to the production of gray cast iron, andhas for its 1 object the further improvement of the physical andmechanical properties thereof.

In cast iron silicon acts as a precipitant of the carbon, driving it outof combination and into graphite form. In fact, the lower the carboncontent of the composition the more silicon is required, although theamount of silicon that can be added is practically limited by variousconsiderations. Thus, for example, a silicon content of much above 1 percent influences deleteriously the structural stability of the cast ironunder high temperatures and hence should not be used for castings ofmachine parts which are subjected to a high degree of heat, such ascylinders and pistons of internal combustion engines, for fire-exposedparts, etc.; and, again, while increases of the silicon content up toabout 3.5 per cent increase the amount of gra hite precipitate, inhigher percentages its influence is reversed and it-then produces aprecipitation, not of graphite, but of various combined carbons.

Gray cast iron with a carbon content below 3 per cent and a siliconcontent of less than 1 per cent has never heretofore been produced, atleast on any practical commercial scale. I have discovered however, asthe result of recent investigations, not only that nickel also acts, andin the same way as silicon, as a precipitant of graphite, but, further,that if the silicon heretofore required for the purpose is partially orwholly replaced by a substantially equal amount of nickel I am able tocut down the total carbon content of gray cast iron to approximately 1.7per cent. Because of the impossibility, in normal practice, of effectinga precipitation of carbon as graphite in iron-carbon compositions inwhich the carbonoontent lies between 1.7 and 2.2 per cent, compositionswith such carbon content have always been regarded as belonging to thesteel groups. In steel, however, it is the rule to keep the carboncontent below 1.7 per cent, and hence compositions Application filed May15, 1924. Serial No. 713,605.

with carbon content between the limits mentioned have never beenpractically used. On the other hand, it is known that the lower thecarbon content of cast iron the higher ,will be its physical andmechanical properties.

My invention accordingly comprises both a new process and a new product.

The process consists, first, in adjusting the composition to a carboncontent below the limit heretofore considered permissible for gray castiron and which may be reduced to approximately 1.7 per cent, and then ineffecting the required precipitation of graphite by the addition ofnickel instead of an increase in the percentage of silicon. For example,in a mixture with a low carbon content which would ordinarily call for1.7 per cent of silicon I replace about half of the silicon with anequal amount of nickel, using 0.9 per cent only of silicon and 0.8 percent of nickel.

The gray cast iron thus roduced, containing as it does a total car oncontent of less than 3 per cent and less than 1 per cent of silicon is,ascompared with all previously known forms of gray cast iron,characterized by a very high stability, both structural and as regardsvolume, under high temperatures and, moreover, by its great strength,due to the small carbon content and to the nickel-iron alloy.

Furthermore, by so governing the casting operation in the practice of mynew process, according to the now known pearlite casting method, thatthe nickel, either alone or in conjunction with any silicon present inthe composition,- will precipitate the.

graphite required under cooling conditions suitable for the productionof the pearlite structure I obtain a pearlite nickel cast iron with aminimum of graphite veinings, and consequently a product which isproduced like cast iron and is to be considered as cast iron but whichexhibits the properties of an alloy steel. Thus, in a bar of 80millimeters diameter, for example, a very good pearlite structure isobtained from a mixture containing 2.12 per cent carbon +0.56 per centsilicon +1.07 per cent nickel +0.15'per cent phosphorus +0.08 per centsulphur +0.8 per cent manganese when cast in a sand mould preheatedlto'about 210 centigrade.

by Letters Patent, is-

1. Thep'rocess of producing gray cast iron which comprises preparingacasting mix: ture and introducing thereinnickel m an amount suficientto eflect, in conjunction from a mixture having a content of carbon andof silicon-less than 3 and 1 per centrespectively in which theprecipitation of the graphite required is efi'ecte'd by-the addition ofnickel to the mixture.

4. The processof producing gray cast iron having a total carbon contentof from about 3 to about 1 per cent and a. silicon content of not much1f any over 1 per cent which comprises adding to the casting mixturenickel in amount suificient, in conjunction with the silicon present, toeffect the precipitation of the graphite required.

,5. Gray cast iron whlch is characterized by a relatively low totalcarbon content and in'which the usual silicon content is replaced inwhole or in part by avsubstantially equal amount of nickel. with thesilicon present therein, the precipi- 6. Gray cast' iron having a totalcarbon content of between 3 per cent and 1.7 per cent approximately, asilicon content of not sub stantially more than 1 per cent, and a nickelcontent suflicient in amount to effect the precipitation of the graphiterequired.

7 Gray cast iron which has a total carbon content of from 3 to 1.7 percent and a silicon content of less than 1 per cent and contains nickel,and which is characterized by great strength and a very high stability,both structural and as regards volume, under high temperatures.

Gray pearlite cast iron which contains nickel and has a total carboncontent between 3 and 1.7 per cent, approximately, of whichsubstantially 0.85- per cent is chemically combined with the iron-nickelelements andthe remainder is in the form of finely divided graphite.

KARL srPr.

